I like the drilled tanks, several of my friends have had the overflow box and they have failed and had floods. They can loose suction ater a power outage, when the power is turned back on the water pumps out of the sump and when the OF does not work the extra water goes on the floor.
Both my tanks are drilled on the back, upper corners and they have been running problem free.

Some tanks are drilled on the back -- not the most efficient design IMO.

I had a HOB fuge. Worked ok. But if you've got a properly designed and pre-drilled tank with overflow then that of course is preferred. Which is what I switched to. 75g w HOB to 110g with intank overflow to drilled hole down to 30g wetdry/fuge. The HOB had an intank overflow box that siphoned out water with a big plastic tube. Worked pretty well but it was a pain in the butt to keep balanced to make effective use of the bioballs. Day-to-day balances

runway, unless you get a tank drilled already(reef ready) then the bottom will more then likely be tempered glass, Termpered glass can not be drilled. Getting a predrilled tank can cost more the getting one not drilled and then installing your own holes. Most glass stores drill holes..
I have them about 3" down and 4" in in both upper corners.. I'll try and post a pic later. If you don't have a RR tank IMO this is the bast way to go..

Scho why are the tanks drilled on the back not efficient?? I belong to a club and there are a lot of members who have them set up like this with no problems. I get great flow out of 2, 1" bulk heads returns, I would say almost 1200 gph if I have the elbows adjusted for a fater flow back.
1" hole in bottom will have the same flow as a 1" hole in the back???
Would like to know what info you have that says these are not efficient..

Here's a question for y'all... Is there any mechanical fix to the problem with HOB overflow boxes in case of power failure? Like, maybe using a power source for the sump pump that does not automatically turn back on, maybe you have to start it when you get the syphon going again... or maybe some mechanical restart for the HOB?

I am planning a sump and had "non-pre-drilled" arcrylic tank. Someday I'll upgrade, so I really don't want to take everything out of this one and drill it.